Cache current thread in a reserved register and use it in LoadIsolate

runtime/vm/stub_code_arm64.cc

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
 #if defined(TARGET_ARCH_ARM64)
 
 #include "vm/assembler.h"
 #include "vm/code_generator.h"
 #include "vm/compiler.h"
@@ skipping 752 matching lines @@
   __ BranchPatchable(&stub_code->FixAllocateArrayStubTargetLabel());
 }
 
 
 // Called when invoking Dart code from C++ (VM code).
 // Input parameters:
 //   LR : points to return address.
 //   R0 : entrypoint of the Dart function to call.
 //   R1 : arguments descriptor array.
 //   R2 : arguments array.
-//   R3 : new context containing the current isolate pointer.
+//   R3 : current thread.
 void StubCode::GenerateInvokeDartCodeStub(Assembler* assembler) {
   __ Comment("InvokeDartCodeStub");
 
   // Copy the C stack pointer (R31) into the stack pointer we'll actually use
   // to access the stack, and put the C stack pointer at the stack limit.
   __ SetupDartSP(Isolate::GetSpecifiedStackSize());
   __ EnterFrame(0);
 
   // Save the callee-saved registers.
   for (int i = kAbiFirstPreservedCpuReg; i <= kAbiLastPreservedCpuReg; i++) {
     const Register r = static_cast<Register>(i);
     // We use str instead of the Push macro because we will be pushing the PP
     // register when it is not holding a pool-pointer since we are coming from
     // C++ code.
     __ str(r, Address(SP, -1 * kWordSize, Address::PreIndex));
   }
 
   // Save the bottom 64-bits of callee-saved V registers.
   for (int i = kAbiFirstPreservedFpuReg; i <= kAbiLastPreservedFpuReg; i++) {
     const VRegister r = static_cast<VRegister>(i);
     __ PushDouble(r);
   }
 
   // We now load the pool pointer(PP) as we are about to invoke dart code and we
   // could potentially invoke some intrinsic functions which need the PP to be
   // set up.
   __ LoadPoolPointer(PP);
 
+  // Set up THR, which caches the current thread in Dart code.
+  if (THR != R3) {
+    __ mov(THR, R3);
+  }
   // Load Isolate pointer into temporary register R5.
   __ LoadIsolate(R5, PP);
 
   // Save the current VMTag on the stack.
   __ LoadFromOffset(R4, R5, Isolate::vm_tag_offset(), PP);
   __ Push(R4);
 
   // Mark that the isolate is executing Dart code.
   __ LoadImmediate(R6, VMTag::kDartTagId, PP);
   __ StoreToOffset(R6, R5, Isolate::vm_tag_offset(), PP);
@@ skipping 1164 matching lines @@
 // R5: isolate.
 // Does not return.
 void StubCode::GenerateJumpToExceptionHandlerStub(Assembler* assembler) {
   ASSERT(kExceptionObjectReg == R0);
   ASSERT(kStackTraceObjectReg == R1);
   __ mov(LR, R0);  // Program counter.
   __ mov(SP, R1);  // Stack pointer.
   __ mov(FP, R2);  // Frame_pointer.
   __ mov(R0, R3);  // Exception object.
   __ mov(R1, R4);  // StackTrace object.
+  // TODO(koda): Pass thread instead of isolate.
+  __ LoadFromOffset(THR, R5, Isolate::mutator_thread_offset(), kNoPP);
   // Set the tag.
   __ LoadImmediate(R2, VMTag::kDartTagId, kNoPP);
   __ StoreToOffset(R2, R5, Isolate::vm_tag_offset(), kNoPP);
   // Clear top exit frame.
   __ StoreToOffset(ZR, R5, Isolate::top_exit_frame_info_offset(), kNoPP);
   __ ret();  // Jump to the exception handler code.
 }
 
 
 // Calls to the runtime to optimize the given function.
@@ skipping 184 matching lines @@
 // Result:
 //  R1: entry point.
 void StubCode::GenerateMegamorphicLookupStub(Assembler* assembler) {
   EmitMegamorphicLookup(assembler, R0, R1, R1);
   __ ret();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM64